Stress-induced regulation of N-terminal acetylation controls proteostasis in plants

植物的生长受到环境因素和相应的细胞监测机制的限制，从而进行应激损伤的修复。蛋白质稳态的控制是蛋白质组适应特定压力和替代受损蛋白质的主要参与者。在本项目中，将研究n -乙酰转移酶（Nat）复合物对蛋白质的共翻译修饰在逆境适应中的作用。主要NatA复合物的n端乙酰化影响拟南芥约40%的细胞质蛋白，并对其半衰期有显著影响。基于对干旱胁迫激素脱落酸（ABA）降低拟南芥NatA活性的观察，导致非乙酰化的NatA底物被一种新的nonAc/N-degron更快地翻译和更有效地降解，我们提出n端乙酰化降低是一种信号，可以有效地替代胁迫损伤的蛋白质。这种新的蛋白质印迹的胁迫转导信号可能在蛋白质损伤的胁迫反应中起作用。利用干旱胁迫作为代理，我们将剖析NatA复合体的核心和调控亚基在胁迫诱导的核糖体蛋白印迹中的作用。aba诱导的NatA活性下调将用于鉴定应力调节的NatA底物，并使用选择性核糖体谱分析研究NatA复合物向核糖体新生链复合物的动态招募。aba触发的含nonAc/N-degron蛋白的周转可以通过串联荧光计时器系统在体内成像来定量。含nonAc/N-degron的蛋白质的命运将在基于亲和富集和蛋白质质谱分析的基础上，对泛素-蛋白酶体和自噬介导的降解进行剖析。最后，将评估在NatA活性降低的情况下，传感器激酶TOR在增强翻译中的作用。本实验旨在阐明动态n端乙酰化对蛋白质损伤应激下蛋白质稳态的意义和作用机制。

Growth of plants is limited by environmental factors and corresponding cellular surveillance mechanisms for stress-induced damage repair. The control of protein homeostasis is a major player in the acclimation of the proteome to specific stresses and the replacement of damaged proteins. In this project, the role of the co-translational modification of proteins by N-acetyltransferase (Nat) complexes for acclimation to stress will be investigated. N-terminal acetylation by the major NatA complex affects about 40% of all cytosolic proteins in Arabidopsis with significant effects on their half-life time. Based on the observation that the drought stress hormone abscisic acid (ABA) decreases NatA activity in Arabidopsis, causing faster translation and more efficient degradation of non-acetylated NatA substrates by a novel nonAc/N-degron, we propose that lowered N-terminal acetylation serves as a signal enabling efficient replacement of stress-damaged proteins This novel protein-imprinted stress-transducing signal may generally operate in protein-damaging stress responses. Using drought stress as a proxy, we will dissect the roles of the core and regulatory subunits of the NatA complex for stress-induced protein imprinting at the ribosome. ABA-induced down-regulation of NatA activity will be applied to identify stress-regulated NatA substrates and study the dynamic recruitment of the NatA complex to the ribosome nascent chain complex using selective ribosome profiling. The turnover of ABA-triggered nonAc/N-degron containing proteins can be quantified by in vivo imaging using the tandem fluorescent timer system. The fate of nonAc/N-degron containing proteins is going to be dissected with respect to ubiquitin-proteasome and autophagy-mediated degradation following affinity-based enrichment and protein mass spectrometry. Finally, the role of the sensor kinase TOR for enhanced translation in situations with lowered NatA activity will be assessed. The proposed experiments are expected to clarify the significance and mechanism of action of dynamic N-terminal acetylation for proteostasis under protein-damaging stress.